Conventionally known processes for producing cyclic alcohols by hydration of cyclic olefins include processes of indirect or direct hydration using highly concentrated mineral acids, particularly sulfuric acid. Other homogeneous catalysts that have been proposed for the reaction include aromatic sulfonic acids, as described in Japanese Patent Publication Nos. 8104/68 and 16123/68, heteropolyacids, such as phosphotungstic acid and phosphomolybdic acid, as described in Japanese Patent Application (OPI) No. 9746/78 (the term "OPI" as used herein refers to an "unexamined published application"), and the like.
However, when these homogeneous catalysts are used, the desired cyclic alcohol is present in the catalyst system and is difficult to separate and recover. Also, side reactions may occur to an extent which is more than negligible. Thus, separation and purification of the desired cyclic alcohol becomes difficult. In addition, regeneration of catalysts is impossible once they are deteriorated.
In order to overcome these defects, it has been proposed to use solid catalysts, for example, ion exchange resins are described in Japansese Patent Publication Nos. 15619/63 and 26656/69.
Such ion exchange resins, however, have the problem of reduction in size of the resin by mechanical disintegration, and problem of reduction in catalytic activity due to insufficient heat resistance of the resin. Thus such ion exchange resins are incapable of providing stable catalytic activity over a long period of time.
Also as a process of using a solid catalyst, it has been proposed to use crystalline aluminosilicates. Crystalline aluminosilicates are insoluble in water and have excellent mechanical strength and heat resistance, and thus would be expected to be utilizable as industrial catalysts. Thus, Japanese Patent Publication No. 45323/72 proposes a process for producing alcohols by hydration of olefins using dealkalized mordenite, clinoptilolite, or faujasite type zeolite as a catalyst.
Japanese Patent Publication No. 45323/72 describes in Example 4 an example of using cyclohexene as a cyclic olefin. According to Example 4, the reaction is conducted in an autoclave at a reaction temperature of from 200.degree. to 210.degree. C. for a reaction time of from 10 to 15 hours to obtain a conversion of water to cyclohexanol of as low as 0.05 to 0.06%. Calculation of the conversion of cyclohexene to cyclohexanol based on the above description gives a conversion of from 0.07 to 0.08%, and, in turn, calculation of the concentration of cyclohexanol in water based on this conversion gives a concentration of about 0.3%. No description appears therein as to selectivity of reacted cyclohexene to cyclohexanol and formation of by-products. To the contrary, with the hydration reaction of propylene or 1-butene also described in the same Example, although the reaction times are short, conversions of these straight chain olefins to corresponding alcohols are as high as 10 to 20% and 4 to 7%, respectively (calculated based on the conversions of water as in the above-described case, with the concentrations of the resulting alcohols in water, calculated based on these conversions, being 9 to 20% and 4 to 6%, respectively). Thus, the Example shows that hydration of cyclohexene to cyclohexanol is not practical due to too low a conversion to cyclohexanol as compared with the hydration of straight chain olefins.
U.S. Pat. No. 4,214,107 describes examples of gaseous phase catalytic hydration reaction of straight chain olefins, such as ethylene, propylene, etc., using HZSM-5 (proton-exchanged ZSM-5, made by Mobil Oil Corporation). However, no description are found therein with respect to cycloolefins.
U.S. Pat. No. 4,324,940 proposes a process of selectively reacting smaller olefins by effecting acid-catalyzed reactions of a mixed stream composed of smaller olefins and larger olefins having a crystalline zeolite. According to the description in this patent, the acid-catalyzed reactions include hydration reactions, and the olefins include cycloolefins. However, no examples thereof are given therein.
Japanese Patent Application (OPI) No. 70828/82 proposes a process for producing alcohols by hydration of olefins using specific crystalline aluminosilicates of Mobile Oil Corporation, such as ZSM-5 or ZSM-21. However, no examples of reacting cyclic olefins as olefins are given therein. Example 1 shows a reaction of propylene as a straight chain olefin, wherein the reaction is conducted at 200.degree. C. for 2 hours followed by an after-treatment of removing unreacted propylene and the catalyst to obtain an aqueous filtrate containing 8.7 wt% isopropanol. On the other hand, Example 3 shows a reaction of 1-butene, wherein the reaction is conducted at 160.degree. C. for 2 hours, followed by the same after-treatment as described above, to obtain an aqueous filtrate containing as low as 1.2 wt% sec-butyl alcohol.
Japanese Patent Application (OPI) No. 124723/83 proposes a process for producing alcohols by hydration of olefins using, as a catalyst, a partly dealuminated zeolite whose exchangeable ions have been wholly or partly exchanged with a hydrogen ion, or an ion of an element of the group II, VII or VIII of the Periodic Table, or of an earth metal element or rare earth element. However, reaction examples on cyclic olefins are not described therein. As examples of straight chain olefins, Example 1 shows a reaction of n-butylene, wherein the reaction is conducted at 170.degree. C. for 2 hours, followed by removing unreacted n-butylene and the catalyst to obtain a filtrate containing at most 3.4 wt% sec-butyl alcohol.
Other processes proposed for hydration of olefins using crystalline aluminosilicates as catalysts include a process of using offretite as described in Japanese Patent Application (OPI) No. 70630/84, a process of using ferrierite as described in Japanese Patent Application (OPI) No. 70631/84, and a process of using erionite as described in Japanese Patent Application (OPI) No. 144723/84. However, none of these patent applications describes cyclic olefins as olefins to be reacted.
In view of the difference in reactivity between straight chain olefins and cyclic olefins shown in Japanese Patent Application (OPI) No. 4532/72 and the difference in reactivity among straight chain olefins shown in the Examples therein, extremely low reactivity is expected in the synthesis of cyclic alcohols from cyclic olefins using the catalysts specified by the aforesaid U.S. Pat. Nos. 4,214,107 and 4,324,940 and Japanese Patent Application (OPI) Nos. 70828/82, 124723/83, 124723/83, 70630/84, 70631/84 and 144723/84. In addition, side reactions that may occur in the above-described synthesis are unpredictable.
Thus, the above-described conventional processes, when applied to hydration of cyclic olefins, fail to achieve industrially sufficient catalytic activity, and require elevation of the reaction temperature for attaining an industrially satisfactory reaction rate. However, the hydration of cyclic olefins is an exothermic reaction, and the proportion of cyclic alcohols to cyclic olefins in the equilibrium composition decreases with increasing temperature. Therefore, a rise in the reaction temperature brings about reduction of concentrations of the desired cyclic alcohols, which necessitates a high cost for separation and recovery of cyclic alcohols. In addition, a rise of the reaction temperature leads to an increase of not only the hydration rate of cyclic olefins but also a conversion of cyclic alcohols to by-products due to isomerization and the like, resulting in reduction of selectivity to the desired reaction.